/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.socket.sockjs.frame;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Represents a SockJS frame. Provides factory methods to create SockJS frames.
 *
 * @author Rossen Stoyanchev
 * @since 4.0
 */
public class SockJsFrame {

    /**
     * The charset used by SockJS.
     */
    public static final Charset CHARSET = StandardCharsets.UTF_8;

    private static final SockJsFrame OPEN_FRAME = new SockJsFrame("o");

    private static final SockJsFrame HEARTBEAT_FRAME = new SockJsFrame("h");

    private static final SockJsFrame CLOSE_GO_AWAY_FRAME = closeFrame(3000, "Go away!");

    private static final SockJsFrame CLOSE_ANOTHER_CONNECTION_OPEN_FRAME =
            closeFrame(2010, "Another connection still open");


    private final SockJsFrameType type;

    private final String content;


    /**
     * Create a new instance frame with the given frame content.
     *
     * @param content the content (must be a non-empty and represent a valid SockJS frame)
     */
    public SockJsFrame(String content) {
        Assert.hasText(content, "Content must not be empty");
        if ("o".equals(content)) {
            this.type = SockJsFrameType.OPEN;
            this.content = content;
        }
        else if ("h".equals(content)) {
            this.type = SockJsFrameType.HEARTBEAT;
            this.content = content;
        }
        else if (content.charAt(0) == 'a') {
            this.type = SockJsFrameType.MESSAGE;
            this.content = (content.length() > 1 ? content : "a[]");
        }
        else if (content.charAt(0) == 'm') {
            this.type = SockJsFrameType.MESSAGE;
            this.content = (content.length() > 1 ? content : "null");
        }
        else if (content.charAt(0) == 'c') {
            this.type = SockJsFrameType.CLOSE;
            this.content = (content.length() > 1 ? content : "c[]");
        }
        else {
            throw new IllegalArgumentException("Unexpected SockJS frame type in content \"" + content + "\"");
        }
    }

    public static SockJsFrame openFrame() {
        return OPEN_FRAME;
    }

    public static SockJsFrame heartbeatFrame() {
        return HEARTBEAT_FRAME;
    }

    public static SockJsFrame messageFrame(SockJsMessageCodec codec, String... messages) {
        String encoded = codec.encode(messages);
        return new SockJsFrame(encoded);
    }

    public static SockJsFrame closeFrameGoAway() {
        return CLOSE_GO_AWAY_FRAME;
    }

    public static SockJsFrame closeFrameAnotherConnectionOpen() {
        return CLOSE_ANOTHER_CONNECTION_OPEN_FRAME;
    }

    public static SockJsFrame closeFrame(int code, @Nullable String reason) {
        return new SockJsFrame("c[" + code + ",\"" + (reason != null ? reason : "") + "\"]");
    }

    /**
     * Return the SockJS frame type.
     */
    public SockJsFrameType getType() {
        return this.type;
    }

    /**
     * Return the SockJS frame content (never {@code null}).
     */
    public String getContent() {
        return this.content;
    }

    /**
     * Return the SockJS frame content as a byte array.
     */
    public byte[] getContentBytes() {
        return this.content.getBytes(CHARSET);
    }

    /**
     * Return data contained in a SockJS "message" and "close" frames. Otherwise
     * for SockJS "open" and "close" frames, which do not contain data, return
     * {@code null}.
     */
    @Nullable
    public String getFrameData() {
        if (getType() == SockJsFrameType.OPEN || getType() == SockJsFrameType.HEARTBEAT) {
            return null;
        }
        else {
            return getContent().substring(1);
        }
    }

    @Override
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof SockJsFrame)) {
            return false;
        }
        SockJsFrame otherFrame = (SockJsFrame) other;
        return (this.type.equals(otherFrame.type) && this.content.equals(otherFrame.content));
    }

    @Override
    public int hashCode() {
        return this.content.hashCode();
    }

    @Override
    public String toString() {
        String result = this.content;
        if (result.length() > 80) {
            result = result.substring(0, 80) + "...(truncated)";
        }
        result = StringUtils.replace(result, "\n", "\\n");
        result = StringUtils.replace(result, "\r", "\\r");
        return "SockJsFrame content='" + result + "'";
    }

}
